Cesium-137 is part of the nuclear waste produced by uranium-235 fission. The half-life of cesium-137 is 30.2 years. How much time is required for the activity of a sample of cesium-137 to fall to 9.32 percent of its original value

t(9.32% remaining) = 203 yrs (3 sig. figs.)

Explanation:

All radioactive decay follows a 1st order decay profile. This is defined by the expression ...

A =A₀e^-k·t

A = final activity = 9.32%

A₀ = initial activity = 100%

e = base of natural logs

k = rate constant = 0.693/t(1/2) = (0.693/30.2) yrs⁻¹ = 0.023 yrs⁻¹

t = time of decay = ln(A/A₀)/-k = ln(9.32%/100%)/-0.023 yrs⁻¹

 = 203.286637 yrs (calc. ans.)

 ≅ 203 yrs (3 sig. figs.)

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."

answer; protein;